<!DOCTYPE html>
<html>
	<head>
		<!-- 设置编码格式 -->
		<meta charset="utf-8">
		<!-- 手机，移动端开发，需要加的meta标签 -->
		<meta name="viewport" content="initial-scale=1.0,user-scalable=no,maximum-scale=1,width=device-width">
		<style>
			body {
				background-color: lightgreen;
			}
			@media screen and (max-width: 500px) {
				body {
					background-color: lightblue;
					/*禁止手机浏览器下拉刷新*/
					overflow:hidden;
				}
			}
		</style>
	</head>
	<body>
		<h2>当浏览器窗口的宽度小于 500 像素时，背景颜色会变成淡蓝，否则是淡绿色。</h2>
	</body>
</html>
